Traces first (CLAUDE.md); ipx-web traces its requests (#213)

Caddy's tracing directive, switched by WEB_TRACING so a server without a collector does not log
a failed export every few seconds. It continues an incoming traceparent (the page starts one per
tap, #190) and passes it to ipx, so a request is one trace from the browser through Caddy into
ipx, and Caddy's access log carries its traceID. Checked against Tempo with a probe container:
service.name and deployment.environment.name come from the OTEL_ variables, over OTLP/HTTP.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

CLAUDE.md

@@ -273,6 +273,13 @@ set `version` to the next patch with `-dev` (after 0.9.0, `0.9.1-dev`), so a bui
 in the logo's tooltip instead of claiming to be the last release. The release that follows can
 still be a minor or major one; `-dev` only says the work comes after `X.Y.Z`.
 
+**Traces first, logs second.** Anything that does work (a service, a handler, a job, a call to
+another service) gets spans, and passes `traceparent` on to whatever it calls, so one trace in
+Tempo follows a request or a job across ipx-web, ipx and the directory. A trace shows where the
+time went and what called what; a log line only that something happened. Log what a trace cannot
+carry: events worth counting on the dashboard, warnings and errors. A new service or route without
+traces is not finished.
+
 Deliberate simplifications get a `ponytail:` comment naming the ceiling and the upgrade path, e.g.
 `// ponytail: global connection mutex, move to a pool if feed count makes it contend`.